His [Hazrat Mahdi’s (as)] hair is thick, his forehead is broad and there is a slight concavity on his forehead. His nose is small, and there is a very small protrusion right on the bridge. A small mole protrudes on his cheek.

(Bihar Al-Anwar, Vol. 13)

The hadith notes the presence of a small concavity on Hazrat Mahdi’s (as) broad forehead. There will be an unremarkable protrusion in the middle of his small, straight nose. The hadith also says that the mole on Hazrat Mahdi’s (as) cheek will be protruding.